A weary Barbara Boxer took to the Senate floor yesterday evening to offer up a little civics lesson based on her months-long experience conferencing a transportation bill with the House. "I know when our young people learn about how a bill becomes a law, it sounds a little easier than it is," the California Democrat said. But "it's a little trickier than it sounds." That's an understatement, according to descriptions from members and stakeholders, who say that horse trading defined the negotiations between House and Senate members and staff that resulted in a compromise conference report filed late last night.